Types of Types of thermometerthermometer

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AlcoholAlcoholthermometerthermometer

Alcohol thermometerAlcohol thermometer is an alternative to the is an alternative to the mercury-in-glass thermometermercury-in-glass thermometer, and functions in a similar , and functions in a similar way. But unlike mercury-in-glass thermometer, the contents way. But unlike mercury-in-glass thermometer, the contents of an alcohol thermometer are less toxic and will evaporate of an alcohol thermometer are less toxic and will evaporate away fairly quickly. An away fairly quickly. An organic liquidorganic liquid is contained in a is contained in a glass bulb which is connected to a glass bulb which is connected to a capillarycapillary of the same of the same glass and the end is sealed with an expansion bulb. The glass and the end is sealed with an expansion bulb. The space above the liquid is a mixture of nitrogen and the space above the liquid is a mixture of nitrogen and the vapour of the liquid. For the working temperature range, the vapour of the liquid. For the working temperature range, the meniscusmeniscus or interface between the liquid is within the or interface between the liquid is within the capillary. With increasing temperature, the volume of liquid capillary. With increasing temperature, the volume of liquid expands and the expands and the meniscusmeniscus moves up the capillary. The moves up the capillary. The position of the position of the meniscusmeniscus shows the temperature against an shows the temperature against an inscribed scale. It is an important need for science inscribed scale. It is an important need for science experiments.experiments.

Galileo thermometerGalileo thermometer Suspended in the liquid inside the cylinder are a Suspended in the liquid inside the cylinder are a

number of weights. Commonly those weights are number of weights. Commonly those weights are attached to sealed glass bulbs containing colored attached to sealed glass bulbs containing colored liquid for aesthetic effect. As the liquid in the liquid for aesthetic effect. As the liquid in the cylinder changes cylinder changes temperaturetemperature, its , its densitydensity changes changes and the bulbs are free to move – rising or falling to and the bulbs are free to move – rising or falling to reach a position where their density is either equal to reach a position where their density is either equal to that of the surrounding liquid or where they are that of the surrounding liquid or where they are brought to a halt by other bulbs. The bulbs differ in brought to a halt by other bulbs. The bulbs differ in density by a very small amount and are ordered such density by a very small amount and are ordered such that the least dense is at the top and densest at the that the least dense is at the top and densest at the bottom so that they form a temperature scale.bottom so that they form a temperature scale.

Clinical thermometerClinical thermometer The traditional thermometer is a glass tube with a bulb at one end The traditional thermometer is a glass tube with a bulb at one end

containing a liquid which expands in a uniform manner with containing a liquid which expands in a uniform manner with temperature. The tube itself is narrow (capillary) and has calibration temperature. The tube itself is narrow (capillary) and has calibration markings along it. The liquid is often markings along it. The liquid is often mercurymercury, but , but alcohol thermometersalcohol thermometers use a colored alcohol. Medically, a use a colored alcohol. Medically, a maximum thermometermaximum thermometer is often used, which indicates the maximum is often used, which indicates the maximum temperature reached even after it is removed from the body. temperature reached even after it is removed from the body.

To use the thermometer, the bulb is placed in the location where the To use the thermometer, the bulb is placed in the location where the temperature is to be measured and left long enough to be certain to temperature is to be measured and left long enough to be certain to reach reach thermal equilibriumthermal equilibrium—typically three minutes. Maximum-—typically three minutes. Maximum-reading is achieved by means of a constriction in the neck close to the reading is achieved by means of a constriction in the neck close to the bulb. As the temperature of the bulb rises, the liquid expands up the bulb. As the temperature of the bulb rises, the liquid expands up the tube through the constriction. When the temperature falls, the column tube through the constriction. When the temperature falls, the column of liquid breaks at the constriction and cannot return to the bulb, thus of liquid breaks at the constriction and cannot return to the bulb, thus remaining stationary in the tube. After reading the value, the remaining stationary in the tube. After reading the value, the thermometer must be reset by repeatedly swinging it sharply to shake thermometer must be reset by repeatedly swinging it sharply to shake the liquid back through the constriction. the liquid back through the constriction.

Meat thermometerMeat thermometer

A A meat thermometermeat thermometer is a is a thermometerthermometer used to used to measure the internal temperature of measure the internal temperature of meatmeat, especially , especially roasts and roasts and steakssteaks, and other cooked foods. The degree , and other cooked foods. The degree of "doneness" of meat correlates closely with the of "doneness" of meat correlates closely with the internal temperature, so that a thermometer reading internal temperature, so that a thermometer reading indicates when it is cooked as desired. Meat should indicates when it is cooked as desired. Meat should always be cooked so that the interior reaches a always be cooked so that the interior reaches a temperature sufficient to kill pathogens that may temperature sufficient to kill pathogens that may cause cause foodbornefoodborne illness illness; the thermometer helps to ; the thermometer helps to ensure this. ensure this.

Lab thermometerLab thermometer

A A thermometerthermometer (from the (from the GreekGreek θερμόςθερμός, , thermosthermos, , meaning "hot" , is a device that measures temperature or meaning "hot" , is a device that measures temperature or temperature gradient using a variety of different temperature gradient using a variety of different principles.[1] A thermometer has two important principles.[1] A thermometer has two important elements: the temperature sensor (e.g. the bulb on a elements: the temperature sensor (e.g. the bulb on a mercury thermometer) in which some physical change mercury thermometer) in which some physical change occurs with temperature, plus some means of converting occurs with temperature, plus some means of converting this physical change into a numerical value (e.g. the this physical change into a numerical value (e.g. the scale on a mercury thermometer).scale on a mercury thermometer).

There are many types and many uses for thermometers, There are many types and many uses for thermometers, as detailed below in sections of this article.as detailed below in sections of this article.

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